For headphone-less speaker systems directivity of sound is one of the most important characteristics to provide efficient performance of the speakers and three-dimensional perception of sounds by a sound receiver. Directivity is based on the fact that the magnitude of a sound pressure differs depending on direction. There exists a great variety of speaker systems aimed at generation of directional acoustic beams, wherein designs and structures of such system also varies in a wide range depending on specific purpose of the system applications. The speaker systems for directional sound generation, in which the speakers are organized in regular patterns or matrix structure, find wide practical application and are in constant development and improvement. Especially popular and efficient are speaker systems wherein unit sound emitters are represented by piezo emitters. This is because by controlling the intensities and phase of acoustic beams generated by individual piezo emitters it becomes possible not only to create the converging acoustic beams but also to control direction of the beams to a listener or to a specific part of the listener's body, e.g., the head or ears.
On the other hand, known in the art are combined optoacoustic systems in which a plurality of speakers arranged into a regular array for tracking a listener are with the use of optical camera or cameras that assist in finding the position of a listener or listener's body.
For example, U.S. Patent Application Publication No. 20080159571 (Published on July 2008, Inventor: A. Hooley) discloses a portable sound system for use in portable devices such as laptops or mobile phones. The system operates on the principles of parametric sound generation to create a virtual headphone-like system using focusable and steerage beams of ultrasonic sound emitted from a portage phased array or similar source of ultrasonic sound beams, focused at the vicinity of the left and right ear of the user. The system being also capable of producing audible surround sound and adapted to compensate for head motion through use of an optical based tracking system. The platform is fitted with a camera and image-processing software providing at least part of a tracking system as described above. The software analyses the camera captured images when the camera is facing the user of the device and determines from those camera images the location of the head of the user, and from that either deduces the ear positions, or further image analysis is used to measure the ear positions or the general head orientation for subsequent deduction of the ear position, if the latter cannot be directly tracked.
U.S. Patent Application Publication No. 20110129101 (Published on Jun. 2, 2011, Inventor: A. Hooley) discloses a directional microphone system that includes an ultrasonic emitter and receiver. The emitter directs a beam of ultrasound at the audio source with sufficient intensity that non-linear air effects cause non-linear interactions between the ultrasonic sound and the source's sonic sound. Ultrasonic frequency-mired sounds are thereby generated and received by the ultrasonic receiver. Signal processing is carried out on the received signals to strip out the audio signals. The emitter and receiver may be co-located and the emitted beam may be focused at the location of the audio source. The receiver may also be directional acid focusable. The directional microphone system may be very small and yet highly directional at sonic including low audible frequencies. Optimization may be carried out by scanning the beam around, or by using the mobile phone's built-in camera (where fitted) to optically detect the position of the user's mouth, or under user control.
U.S. Patent Application Publication No. 20130121515 (Publication Date: May 16, 2013; Inventors: A. Hooley, et al.) discloses combining a head-tracking system, for example a camera system with a plurality of loudspeakers to enhance the audio experience of the user. The location of the user can be used to alter the audio signal sent to the plurality of loudspeakers to improve such functions as surround sound. In addition, the camera system can be used, when combined with an array of loudspeakers that can produce tight beams of sound, to direct different sound beams at different users, with virtually no crosstalk to allow users to experience different media from the same audio system, and which is tolerant of changed user positions. In addition, the camera system can aid setting up the array for real surround sound delivery, which bounces sound beams off wall. Cross-talk cancellation can additionally be used. The sound beams may represent 2-D or 3-D sound sources in real time. Sound beam parameters are adjusted to provide the listener with in impression of the 2-D or 3-D position and movement of sound-producing entities of audio-visual program material in real-time. The beam parameters used include beam-direction, beam focal length, frequency response and gain. Such a Sound Projector producing a real-time representation of 3-D sound sources can be used alone or in conjunction with a video display, a television, a personal computer or a games console.
U.S. Pat. No. 7,515,719 issued on Apr. 7, 2009 to A. Hooley, et al. discloses a method and apparatus for taking an input signal, replicating it a number of times and modifying each of the replicas before routing them to respective output transducers such that a desired sound field is created. This sound field may comprise a directed beam, focused beam or a simulated origin. In a first aspect, delays are added to sound channels to remove the effects of different travelling distances. In a second aspect, a delay is added to a video signal to account for the delays added to the sound channels. In a third aspect, different window functions are applied to each channel to give improved flexibility of use. In a fourth aspect, a smaller extent of transducers is used top output high frequencies than are used to output low frequencies. An array having a larger density of transducers near the center is also provided. In a fifth aspect, a line of elongate transducers is provided to give good directivity in a plane. In a sixth aspect, sound beams are focused in front or behind surfaces to give different beam widths and simulated origins. In a seventh aspect, a camera is used to indicate where sound is directed.